Carotenoids are essential antioxidant micronutrients. Oviparous species acquire carotenoids from their food and deposit them in the egg yolk, where they support embryonic development. The total carotenoid concentration in the egg yolk is typically measured analytically, which requires time, equipment and expertise, and can limit the sample available for other measurements, at least in species laying small eggs. Here we evaluate whether yolk colour can be used as a reliable alternative measure for total yolk carotenoid concentration. We compare two non‐analytical methods, digital photography and visual colour scoring, using eggs from a wild population of Blue Tits Cyanistes caeruleus. Yolk hue estimated from digital photographs correlated more strongly with total yolk carotenoid concentration measured by high‐performance liquid chromatography (HPLC) than did the visually assessed colour score based on a Yolk Colour Fan. Previous results based on HPLC measurements of total carotenoid concentration could be reproduced using yolk hue measurements. The results suggest that measuring yolk hue is a suitable proxy for assessing natural variation in total yolk carotenoid concentration in eggs of free‐living birds.

中文翻译：

---

非分析方法估算蛇形蛋中总卵黄类胡萝卜素

类胡萝卜素是必需的抗氧化剂微量营养素。卵生动物从食物中获取类胡萝卜素，并将其沉积在蛋黄中，以支持胚胎发育。蛋黄中总类胡萝卜素的浓度通常通过分析来测量，这需要时间，设备和专业知识，并且至少在下小卵的物种中，这可能限制了可用于其他测量的样品。在这里，我们评估蛋黄颜色是否可以用作总蛋黄类胡萝卜素浓度的可靠替代方法。我们使用来自蓝山雀蓝藻野生种群的卵比较了两种非分析方法，即数码摄影和视觉颜色评分。通过数字照片估算出的蛋黄色调与通过高效液相色谱（HPLC）测量的总蛋黄类胡萝卜素浓度的相关性比基于蛋黄颜色风扇的目测评估色标更紧密。基于HPLC测量总类胡萝卜素浓度的先前结果可以使用蛋黄色调测量得到。结果表明，测量卵黄色调是评估自由生存鸟卵中总卵黄类胡萝卜素浓度自然变化的合适替代方法。